android - 在 ListView Android 中下载多个带有进度条的文件

Question

我想创建一个 ListView 允许用户下载许多文件并在每个 ListView 项目中显示进度条状态。它看起来像这样:

下载ListView有一些规则:

• 每个下载任务都显示在一个 ListView 项目中，带有进度条、百分比和当前状态(正在下载、等待、已完成)。
• 最多允许 5 个下载任务，其他任务需要等待
• 用户可以取消下载任务，并将该任务从ListView
中移除
• ListView 在下载 Activity 中。用户可以更改为另一个 Activity 。当他们离开时，继续在后台下载。当他们回来时，显示下载任务的当前进度和状态。
• 保留已完成的下载任务，直到用户想要删除它们。

我尝试在 Service 中使用 ThreadPoolExcutor。对于每个下载任务，我可以获得完成百分比，但我不知道如何将它们广播到适配器以显示进度。而且我不知道如何让所有任务在后台运行，然后在包含 ListView 的 Activity 处于 Activity 状态时发布进度并保持已完成的任务
如果有任何库或示例可以解决我的问题，那就太好了。提前致谢!P/S:我已经搜索过类似的问题，但我找不到这个问题的解决方案，所以我不得不详细创建自己的问题。所以请不要将其标记为duplicate。谢谢。

Answer 1

这是一个工作示例，请看一下。

启动应用，按返回键，然后再次返回，测试启动另一个Activity并返回的情况。

确保为您的 IntentService 获取 PARTIAL_WAKE_LOCK 以确保 CPU 继续运行。

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import android.app.Activity;
import android.app.IntentService;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
import android.support.v4.content.LocalBroadcastManager;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

public class MainActivity extends Activity {
    public static final String ID = "id";
    private ListView mListView;
    private ArrayAdapter<File> mAdapter;
    private boolean mReceiversRegistered;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ListView listView = mListView = (ListView) findViewById(R.id.list);
        long id = 0;
        File[] files = {getFile(id++),
                getFile(id++), getFile(id++), getFile(id++),
                getFile(id++), getFile(id++), getFile(id++),
                getFile(id++), getFile(id++), getFile(id++),
                getFile(id++), getFile(id++), getFile(id++),
                getFile(id++), getFile(id++), getFile(id++),
                getFile(id++), getFile(id++), getFile(id++),
                getFile(id++), getFile(id++), getFile(id++),
                getFile(id++), getFile(id++), getFile(id++),
                getFile(id++), getFile(id++), getFile(id)};
        listView.setAdapter(mAdapter = new ArrayAdapter<File>(this,
                R.layout.row, R.id.textView, files) {
            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                View v = super.getView(position, convertView, parent);
                updateRow(getItem(position), v);
                return v;
            }
        });

        if (savedInstanceState == null) {
            Intent intent = new Intent(this, DownloadingService.class);
            intent.putParcelableArrayListExtra("files", new ArrayList<File>(Arrays.asList(files)));
            startService(intent);
        }

        registerReceiver();
    }

    private File getFile(long id) {
        return new File(id, "https://someurl/" + id);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver();
    }

    private void registerReceiver() {
        unregisterReceiver();
        IntentFilter intentToReceiveFilter = new IntentFilter();
        intentToReceiveFilter
                .addAction(DownloadingService.PROGRESS_UPDATE_ACTION);
        LocalBroadcastManager.getInstance(this).registerReceiver(
                mDownloadingProgressReceiver, intentToReceiveFilter);
        mReceiversRegistered = true;
    }

    private void unregisterReceiver() {
        if (mReceiversRegistered) {
            LocalBroadcastManager.getInstance(this).unregisterReceiver(
                    mDownloadingProgressReceiver);
            mReceiversRegistered = false;
        }
    }

    private void updateRow(final File file, View v) {
        ProgressBar bar = (ProgressBar) v.findViewById(R.id.progressBar);
        bar.setProgress(file.progress);
        TextView tv = (TextView) v.findViewById(R.id.textView);
        tv.setText(file.toString());
        v.findViewById(R.id.cancel).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent();
                i.setAction(DownloadingService.ACTION_CANCEL_DOWNLOAD);
                i.putExtra(ID, file.getId());
                LocalBroadcastManager.getInstance(MainActivity.this).sendBroadcast(i);
            }
        });
    }

    // don't call notifyDatasetChanged() too frequently, have a look at
    // following url http://stackoverflow.com/a/19090832/1112882
    protected void onProgressUpdate(int position, int progress) {
        final ListView listView = mListView;
        int first = listView.getFirstVisiblePosition();
        int last = listView.getLastVisiblePosition();
        mAdapter.getItem(position).progress = progress > 100 ? 100 : progress;
        if (position < first || position > last) {
            // just update your data set, UI will be updated automatically in next
            // getView() call
        } else {
            View convertView = mListView.getChildAt(position - first);
            // this is the convertView that you previously returned in getView
            // just fix it (for example:)
            updateRow(mAdapter.getItem(position), convertView);
        }
    }

    protected void onProgressUpdateOneShot(int[] positions, int[] progresses) {
        for (int i = 0; i < positions.length; i++) {
            int position = positions[i];
            int progress = progresses[i];
            onProgressUpdate(position, progress);
        }
    }

    private final BroadcastReceiver mDownloadingProgressReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            if (intent.getAction().equals(
                    DownloadingService.PROGRESS_UPDATE_ACTION)) {
                final boolean oneShot = intent
                        .getBooleanExtra("oneshot", false);
                if (oneShot) {
                    final int[] progresses = intent
                            .getIntArrayExtra("progress");
                    final int[] positions = intent.getIntArrayExtra("position");
                    onProgressUpdateOneShot(positions, progresses);
                } else {
                    final int progress = intent.getIntExtra("progress", -1);
                    final int position = intent.getIntExtra("position", -1);
                    if (position == -1) {
                        return;
                    }
                    onProgressUpdate(position, progress);
                }
            }
        }
    };

    public static class DownloadingService extends IntentService {
        public static String PROGRESS_UPDATE_ACTION = DownloadingService.class
                .getName() + ".progress_update";

        private static final String ACTION_CANCEL_DOWNLOAD = DownloadingService.class
                .getName() + "action_cancel_download";

        private boolean mIsAlreadyRunning;
        private boolean mReceiversRegistered;

        private ExecutorService mExec;
        private CompletionService<NoResultType> mEcs;
        private LocalBroadcastManager mBroadcastManager;
        private List<DownloadTask> mTasks;

        private static final long INTERVAL_BROADCAST = 800;
        private long mLastUpdate = 0;

        public DownloadingService() {
            super("DownloadingService");
            mExec = Executors.newFixedThreadPool( /* only 5 at a time */5);
            mEcs = new ExecutorCompletionService<NoResultType>(mExec);
            mBroadcastManager = LocalBroadcastManager.getInstance(this);
            mTasks = new ArrayList<MainActivity.DownloadingService.DownloadTask>();
        }

        @Override
        public void onCreate() {
            super.onCreate();
            registerReceiver();
        }

        @Override
        public void onDestroy() {
            super.onDestroy();
            unregisterReceiver();
        }

        @Override
        public int onStartCommand(Intent intent, int flags, int startId) {
            if (mIsAlreadyRunning) {
                publishCurrentProgressOneShot(true);
            }
            return super.onStartCommand(intent, flags, startId);
        }

        @Override
        protected void onHandleIntent(Intent intent) {
            if (mIsAlreadyRunning) {
                return;
            }
            mIsAlreadyRunning = true;

            ArrayList<File> files = intent.getParcelableArrayListExtra("files");
            final Collection<DownloadTask> tasks = mTasks;
            int index = 0;
            for (File file : files) {
                DownloadTask yt1 = new DownloadTask(index++, file);
                tasks.add(yt1);
            }

            for (DownloadTask t : tasks) {
                mEcs.submit(t);
            }
            // wait for finish
            int n = tasks.size();
            for (int i = 0; i < n; ++i) {
                NoResultType r;
                try {
                    r = mEcs.take().get();
                    if (r != null) {
                        // use you result here
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
            }
            // send a last broadcast
            publishCurrentProgressOneShot(true);
            mExec.shutdown();
        }

        private void publishCurrentProgressOneShot(boolean forced) {
            if (forced
                    || System.currentTimeMillis() - mLastUpdate > INTERVAL_BROADCAST) {
                mLastUpdate = System.currentTimeMillis();
                final List<DownloadTask> tasks = mTasks;
                int[] positions = new int[tasks.size()];
                int[] progresses = new int[tasks.size()];
                for (int i = 0; i < tasks.size(); i++) {
                    DownloadTask t = tasks.get(i);
                    positions[i] = t.mPosition;
                    progresses[i] = t.mProgress;
                }
                publishProgress(positions, progresses);
            }
        }

        private void publishCurrentProgressOneShot() {
            publishCurrentProgressOneShot(false);
        }

        private synchronized void publishProgress(int[] positions,
                                                  int[] progresses) {
            Intent i = new Intent();
            i.setAction(PROGRESS_UPDATE_ACTION);
            i.putExtra("position", positions);
            i.putExtra("progress", progresses);
            i.putExtra("oneshot", true);
            mBroadcastManager.sendBroadcast(i);
        }

        // following methods can also be used but will cause lots of broadcasts
        private void publishCurrentProgress() {
            final Collection<DownloadTask> tasks = mTasks;
            for (DownloadTask t : tasks) {
                publishProgress(t.mPosition, t.mProgress);
            }
        }

        private synchronized void publishProgress(int position, int progress) {
            Intent i = new Intent();
            i.setAction(PROGRESS_UPDATE_ACTION);
            i.putExtra("progress", progress);
            i.putExtra("position", position);
            mBroadcastManager.sendBroadcast(i);
        }

        class DownloadTask implements Callable<NoResultType> {
            private int mPosition;
            private int mProgress;
            private boolean mCancelled;
            private final File mFile;
            private Random mRand = new Random();

            public DownloadTask(int position, File file) {
                mPosition = position;
                mFile = file;
            }

            @Override
            public NoResultType call() throws Exception {
                while (mProgress < 100 && !mCancelled) {
                    mProgress += mRand.nextInt(5);
                    Thread.sleep(mRand.nextInt(500));

                    // publish progress
                    publishCurrentProgressOneShot();

                    // we can also call publishProgress(int position, int
                    // progress) instead, which will work fine but avoid broadcasts
                    // by aggregating them

                    // publishProgress(mPosition,mProgress);
                }
                return new NoResultType();
            }

            public int getProgress() {
                return mProgress;
            }

            public int getPosition() {
                return mPosition;
            }

            public void cancel() {
                mCancelled = true;
            }
        }


        private void registerReceiver() {
            unregisterReceiver();
            IntentFilter filter = new IntentFilter();
            filter.addAction(DownloadingService.ACTION_CANCEL_DOWNLOAD);
            LocalBroadcastManager.getInstance(this).registerReceiver(
                    mCommunicationReceiver, filter);
            mReceiversRegistered = true;
        }

        private void unregisterReceiver() {
            if (mReceiversRegistered) {
                LocalBroadcastManager.getInstance(this).unregisterReceiver(
                        mCommunicationReceiver);
                mReceiversRegistered = false;
            }
        }

        private final BroadcastReceiver mCommunicationReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                if (intent.getAction().equals(
                        DownloadingService.ACTION_CANCEL_DOWNLOAD)) {
                    final long id = intent.getLongExtra(ID, -1);
                    if (id != -1) {
                        for (DownloadTask task : mTasks) {
                            if (task.mFile.getId() == id) {
                                task.cancel();
                                break;
                            }
                        }
                    }
                }
            }
        };

        class NoResultType {
        }
    }

    public static class File implements Parcelable {
        private final long id;
        private final String url;
        private int progress;

        public File(long id, String url) {
            this.id = id;
            this.url = url;
        }

        public long getId() {
            return id;
        }

        public String getUrl() {
            return url;
        }

        @Override
        public String toString() {
            return url + " " + progress + " %";
        }

        @Override
        public int describeContents() {
            return 0;
        }

        @Override
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeLong(this.id);
            dest.writeString(this.url);
            dest.writeInt(this.progress);
        }

        private File(Parcel in) {
            this.id = in.readLong();
            this.url = in.readString();
            this.progress = in.readInt();
        }

        public static final Parcelable.Creator<File> CREATOR = new Parcelable.Creator<File>() {
            public File createFromParcel(Parcel source) {
                return new File(source);
            }

            public File[] newArray(int size) {
                return new File[size];
            }
        };
    }
}

row.xml 布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Title" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:max="100" />

    <Button
        android:id="@+id/cancel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:text="Cancel" />

</LinearLayout>

activity_main.xml 只包含一个 ListView:

<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/list"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

注意:请务必像这样在 AndroidManifest.xml 中注册 DownloadingService:

<service android:name=".MainActivity$DownloadingService" />

更新:

• 添加了取消支持